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Cellular

Revision as of 17:30, 7 January 2008 by Burfine (talk | contribs) (→‎T-Mobile)
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Welcome! Wireless Wiki is a practical, comprehensive, and objective resource for wireless communications, particularly wireless access to the Internet, and related wireless technologies (e.g., cellular). Founded by John Navas.

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This article covers the practical aspects of wireless access to the Internet via Cellular.

Tip: See also Cellular on a Boat


Stub: This article is a stub. You can help the Wireless Wiki by expanding it.


Introduction to Cellular

This article is specifically about cellular data (including cellular Internet), not cellular voice and other cellular services. For more information on cellular, see Cell Phone Enthusiasts Wiki.

GSM

Global System for Mobile Communications (GSM) is a digital cellular communications technology based on Time Division Multiple Access (TDMA), and is the dominant mobile communications system in most of the world, including Europe, the Middle East, Africa, and Asia, and it now has a strong presence in North America as well. First introduced in 1991, the GSM standard has been deployed in four different frequency bands: 800 (called "850" so as not to be confused with D-AMPS on 800), 900, 1800, and 1900 MHz. GSM 850 and 1900 are primarily used in North America; GSM 900 and 1800 are primarily used outside of North America. GSM uses narrowband TDMA that allows up to eight (or sixteen with Half-Rate Codec[1]) simultaneous calls on the same radio frequency using different time slots in the same channel. Along with CDMA and D-AMPS (Digital AMPS, often referred to simply as "TDMA"), GSM represents the 2nd generation (2G) of cellular wireless.

CSD

CSD (Circuit Switched Data) is similar to dialup modem communications. However, a GSM phone has no real modem, just a sort of virtual modem which makes a connection to a carrier's IWU (Inter-Working Unit), located in a service center. The IWU has the actual modem that makes analog data calls and/or fax calls over the PSTN (public switched telephone network). If the carrier doesn't provide the IWU facility, or if the account isn't provisioned for CSD, then a GSM phone cannot make data and/or fax calls.
Speed of CSD is 9.6 Kbps.
A regular dialup modem cannot be made to work over a GSM voice channel because of the audio data compression used.

HSCSD

GPRS

With a Class 10 device and good signal, typical download speeds of about 50 Kbps (about 6K Bytes/sec). Available in most GSM service areas.

EGPRS(EDGE)

With a Class 10 device and good signal, typical download speeds of about 150 Kbps (about 18.5K Bytes/sec). Latency (as measured by ping) of about 300 ms. Widely available. Backward compatible to GPRS.

UMTS

Typical download speeds of 200-320 Kbps (or about 2x EGPRS). Most (but not all; e.g., Novatel U520) devices are backward compatible to EGPRS and GPRS.

HSPA

Typical speeds are currently 400-700 Kbps (or about 4x EGPRS). Latency (as measured by ping) is about 150 ms (or about 1/2 EGPRS). Backward compatible to UMTS, EGPRS and GPRS.

CDMA

1xRTT

Round-trip latency of about 350 ms.

EV-DO

EV-DO Rev. A

Carriers

AT&T, Formerly Cingular

Sprint/Nextel

T-Mobile USA

Verizon

WAP

Wireless Application Protocol (WAP) is a protocol for wireless Internet access that is designed for small screen cellular phones. Access to the Internet is through a WAP Gateway.

WAP Gateways

Ceullular Modems

GSM/UMTS/HSPA

CDMA

Wireless Broadband Routers

Tip: Use of EV-DO data service as a non-mobile DSL/cable modem replacement may be against the terms of service of a given carrier (e.g., Verizon).

Footnotes and References

  1. ↑ Initial public perception of Half-Rate Codec quality was so poor that it's not been generally used. However, adaptive encoding has improved quality substantially since then, so it's possible that Half-Rate Codec may be used more widely in the future, particularly in highly cost-sensitive markets (e.g., less developed countries).

External links

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